1. Field of the Invention
The present invention relates to the application, in an intervertebral stabilization device, of certain dampers comprising means for progressively resisting in exponential manner the advance of a piston under the effect of a force of axial compression.
2. History of the Related Art
Such dampers are well known in the automobile domain. For example, U.S. Pat. No. 3,904,226 and NL-279 186 each describe a single- or double-effect damper which is capable of progressively resisting, in exponential manner, the advance of the piston, so that, after a certain stroke of the piston, the damper opposes any displacement of the piston beyond a determined value of the displacement.
To that end, the damper contains, between a bottom of a cylinder and a piston, an elastic body whose volume is smaller than that of a chamber determined by the position in the free state of the piston with respect to the bottom of the cylinder.
Such a damper is a so-called single-effect damper, i.e. it functions only in one direction. If a double-effect damper is desired, i.e. acting in two opposite directions, it suffices to place a second elastic body in the compartment located between the piston and a cover closing the cylinder opposite its bottom, in which the second elastic body has a volume smaller than that of the compartment.